**Question:** Which of the following potassium sparing diuretics cause renal stones?

A. Spironolactone
B. Amiloride
C. Triamterene
D. Furosemide

**Core Concept:** Potassium sparing diuretics are medications that prevent the loss of potassium ions in the urine while increasing the excretion of other electrolytes, such as sodium and water. They are commonly used in the management of hypertension and edema.

**Why the Correct Answer is Right:** Potassium sparing diuretic triamterene causes renal stones due to its ability to increase the excretion of calcium and uric acid in the urine. This leads to a higher concentration of these ions in the urine, which can promote the formation of renal stones, particularly calcium stones and urate stones.

**Why Each Wrong Option is Incorrect:**

A. Spironolactone: This medication is also a potassium sparing diuretic, but it does not significantly increase the excretion of calcium and uric acid, reducing its potential for causing renal stones compared to triamterene.

B. Amiloride: Amiloride is a potassium sparing diuretic as well, but its mechanism of action is different from triamterene. Unlike triamterene, amiloride primarily inhibits sodium reabsorption in the distal convoluted tubule, which results in a milder impact on calcium and uric acid excretion, further reducing its association with renal stones.

C. Furosemide: Furosemide is a loop diuretic, not a potassium sparing diuretic. It primarily targets the loop of Henle in the nephron, inhibiting sodium reabsorption and increasing urine output. Therefore, it does not significantly impact calcium and uric acid excretion, making it less likely to cause renal stones compared to triamterene and amiloride.

**Clinical Pearl:** It is essential for healthcare professionals to be aware of the potential side effects of certain medications, especially when prescribing them. In the context of renal stones, understanding the mechanism of action for each potassium sparing diuretic can help prevent or identify complications associated with their use.

**Correct Answer:** Triamterene (C)

---

**Core Concept:** Renal stones, also known as urolithiasis, are mineral-based concretions that form in the kidneys and can obstruct the urinary tract, leading to severe complications. They are classified into different types, such as calcium, uric acid, cystine, and mixed stones.

**Why the Correct Answer is Right:** Triamterene, a potassium sparing diuretic, increases calcium and uric acid excretion in urine, thereby increasing the risk of renal stone formation. The increased calcium and uric acid excretion leads to a higher concentration of these substances in the urine, promoting the formation of calcium and uric acid stones.

**Why Each Wrong Option is Incorrect:**

A. Spironolactone (Spironolactone is not included in the options, but it is worth mentioning that it is a potassium sparing diuretic with a similar